The genetics of adaptive racial differences between races of the mutually mimetic butterflies, Heliconius melpomene and Heliconius erato, is being investigated with special reference to: a. the occurrence and causes of 'beanbag' evolution; b. the role of linkage in this process; c. the influence of the naturally selected solour pattern genes in evolution of loci controlling allozymes. We are investigating the genetic control of recombination in silkworms.